Risk factors are characteristics or conditions that increase the likelihood of developing a disease. These can be classified into: 1. Biological Factors: Age, gender, genetic predisposition. 2. Behavioral Factors: Smoking, alcohol consumption, physical inactivity. 3. Environmental Factors: Exposure to pollutants, climate change. 4. Socioeconomic Factors: Income, education, occupation. Studying these risk factors helps in identifying vulnerable populations and developing targeted prevention strategies.